The MR21-0010-20 from MAST Technologies is a Microwave Absorber with Frequency 1 to 3 GHz, Thickness 0.125 Inch/3.2 mm, Thickness 0.125 Inch, Thickness (mm) 3.2 mm, Operating Temperature -60 Degrees F to 375 Degrees F. Tags: Cavity Resonance Absorber. More details for MR21-0010-20 can be seen below.